Ferroelectric capacitors have potential use as decoupling or voltage-tunable capacitors (varactors) in RF systems. Some benefits of ferroelectric capacitors are small size, integration of different values and functions of capacitance, and low cost. Applications for ferroelectric capacitors may include tunable filters, voltage-controlled oscillators, tunable phase shifters, tunable matching networks, low-impedance power supplies, decoupling high-frequency signals at an IC bonding pad, or others. Integrated circuits including ferroelectric capacitors may, for example, be used in portable electronics for low-power wireless communication (e.g., cellular phones, pagers, PDAs, etc.), directional antenna systems, high clock-rate microphones, miniature DC to DC converters, or other devices.
A ferroelectric capacitor may be fabricated by depositing a ferroelectric film on an electrode layer and then depositing a second electrode layer over the ferroelectric film. The deposition technique can be sputtering, chemical vapor deposition (CVD) of any kind (including ALD and CCVD), or pulsed laser deposition (PLD). The ferroelectric film can be Barium Strontium Titanate (BST), Strontium Bismuth Tantalate (SBT), Lead Zirconate Titanate (PZT), Lead Lanthanum Zirconate Titanate (PLZT) or any other perovskite or pyrochlore phase ferroelectric film or a combination thereof. The electrode can be made of any metal or conductive oxide or any combination of these materials. Preferred in this embodiment is Platinum, Platinum alloy, Iridium either solely or in combination with Iridium Oxide, Ruthenium Oxide, or Strontium Ruthenium Oxide (SRO). Sputtered ferroelectric films have a columnar morphology with a pronounced preferential orientation that is perpendicular to the electrodes. As a result, sputter deposited perovskite films have a high tuning and capacitance density. However, the TDDB behavior of the ferroelectric capacitor is adversely affected by the crystalline columnarity of the ferroelectric film because grain boundaries are aligned perpendicular to the electrodes. The technology described herein provides a modification to the columnarity of the sputtered ferroelectric film, which breaks up charged carrier migration through the film and thus improves the TDDB of the capacitor.